1. Field of the Art
The present invention relates to improvements in a multicolor or full-color liquid crystal display panel capable of effecting a color display of images by utilizing a liquid crystal material.
2. Related Art Statement
A pocket-sized or pocketable color-TV set is known, which uses a multicolor liquid crystal display panel. Such a liquid crystal display panel comprises: two transparent substrate sheets of glass; picture-element electrodes and a thin-film transistor (TFT) circuit which are formed on one of the two glass sheets; a color filter layer in the form of a checkered board consisting of red, blue and green filters which are formed on the other of the two glass sheets so as to provide individual picture elements (smallest divisions of an image); and a liquid crystal layer of twisted nematic type which is sealed in between the two glass sheets. It is needless to point out that the performance of this type of multicolor liquid crystal display panel depends largely upon an arrangement of the transistor circuit and the properties of the liquid crystal material used. For better performance of the display panel, however, considerations should also be given to the properties of the material of the transparent substrate glass sheets, which have appreciable effects on the quality of a display on the display panel. Namely, the glass material used for the transparent substrate sheets must meet various requirements. Firstly, the glass sheets should be substantially achromatic or transparent, having a high degree of transparency to the visible rays of light (in the visible region of wavelengths), in order to assure a clear color display of images, since the color display is accomplished by controlling amounts of light transmitted through individual parts or areas of the liquid crystal layer corresponding to the picture elements. The second requirement of the substrate glass sheets is concerned with a heat treatment process at a temperature around 600.degree. C. during the manufacture of the panel, more precisely, in forming the picture-element electrodes and the thin-film transistor circuit. In this process of manufacture, the glass material must be free of deformation or cracks due to exposure to heat during the heat treatments. In the meantime, a thermal expansion of the transparent glass sheets will cause changes in electrical resistance and other properties of the thin-film transistors. To avoid such unfavourable changes, the glass material for the transparent substrate sheets must have a coefficient of thermal expansion as low as about 5.times.10.sup.-7 /.degree.C. This is the third requirement of the glass material for the transparent substrate sheets of the display panel. A conventional multicolor liquid crystal display panel uses quartz glass, as a glass material that satsifies the above-addressed requirements. The liquid crystal display panels with transparent substrates of quartz glass are found satsifactory for the most part in their performance of display.